The present disclosure relates generally to methods and systems for performing oilfield operations. More particularly, the present disclosure relates to methods and systems for performing stimulation operations, such as investigating subterranean formations, characterizing hydraulic fracture networks in a subterranean formation, and generating stimulation plans.
The statements made herein merely provide information related to the present disclosure and may not constitute prior art, and may describe some embodiments illustrating the invention.
In order to facilitate the recovery of hydrocarbons from oil and gas wells, the subterranean formations surrounding such wells can be hydraulically fractured. Hydraulic fracturing has become a valuable technique to create cracks in subsurface formations that allow hydrocarbons to move toward the well. Hydraulic fractures may extend away from the wellbore hundreds of feet in two opposing directions according to the natural stresses within the formation. Under certain circumstances, they may form a complex fracture network. Complex fracture networks can include induced hydraulic fractures and natural fractures, which may or may not intersect, along multiple azimuths, in multiple planes and directions, and in multiple regions.
A formation is fractured by introducing a specially engineered fluid (referred to as “fracturing fluid” or “fracturing slurry”) at high pressure and high flow rates into the formation through one or more wellbores. Oilfield service companies have developed a number of different oil- and water-based fluids and treatments to more efficiently induce and maintain permeable and productive fractures. The composition of these fluids varies significantly, from simple water and sand to complex polymeric substances with a multitude of additives. Each type of fracturing fluid has unique characteristics, and each possesses its own positive and negative performance traits. It is desirable to selectively modify certain qualities of the fracturing fluid, and pumping characteristics, to achieve a desired complexity of the fracture network.
For example, a highly complex fracture network geometry with tortuous fractures, multiple kinking and changes in fracture directions may make the fracture opening too narrow or create pinch points that hampers hydrocarbon or particle transport. To achieve better production of fractured reservoirs, it is desirable to create relatively straight and open hydraulic fractures.
In some cases, the occurrence of fractures and the extent of the fractures in the formation may be numerically modeled to infer hydraulic fracture propagation over time. Conventional hydraulic fracture models typically assume a bi-wing type induced fracture. These bi-wing fractures may be short in representing the complex nature of induced fractures in some unconventional reservoirs with pre-existing discontinuities, such as natural fractures (NF). Moreover, while some commercially available fracture models may take into account pre-existing natural fractures in the formation, many of the published models are oversimplified and neglect to account for the rigorous elastic solution of the interaction between induced fractures and natural fractures. Further, the vast majority of published models do not explicitly take into account the pumping properties of the fluid, which may include the injection rate, viscous properties of the fluid, and concentration of fluid additives.